Exodus 6:27-31

They were the ones who spoke to Pharaoh king of Egypt about bringing out the sons of Israel from Egypt; it was the same Moses and Aaron.

Now it came about on the day when the Lord spoke to Moses in the land of Egypt,

that the Lord spoke to Moses, saying, “I am the Lord; say to Pharaoh king of Egypt all that I say to you.”

But Moses said before the Lord, “Behold, I am unskilled in speech; how then will Pharaoh listen to me?”